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From "Yan Zhou (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1399) Logical Optimizer: Expression optimizor rule
Date Tue, 13 Jul 2010 18:25:53 GMT

    [ https://issues.apache.org/jira/browse/PIG-1399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12887912#action_12887912
] 

Yan Zhou commented on PIG-1399:
-------------------------------

A couple of additional scenarios to be simplified:

5.  equality
Example:
B = filter A by (a0 > 5 and a0 > 5);
=> B = filter A by a0 > 5;


6. complementary OR
Example:
B = filter A by (a0 > 5 OR a0 <= 5);
=> the filtering is removed

Note that by themselves they both look straightforward and may have little value. But used
after other simplification rules, it could simplify the end results further but could be not
obviously applicable at first place.

> Logical Optimizer: Expression optimizor rule
> --------------------------------------------
>
>                 Key: PIG-1399
>                 URL: https://issues.apache.org/jira/browse/PIG-1399
>             Project: Pig
>          Issue Type: Sub-task
>          Components: impl
>    Affects Versions: 0.7.0
>            Reporter: Daniel Dai
>            Assignee: Yan Zhou
>             Fix For: 0.8.0
>
>
> We can optimize expression in several ways:
> 1. Constant pre-calculation
> Example:
> B = filter A by a0 > 5+7;
> => B = filter A by a0 > 12;
> 2. Boolean expression optimization
> Example:
> B = filter A by not (not(a0>5) or a>10);
> => B = filter A by a0>5 and a<=10;

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